light switches

[sinnadurai sripadmanaban]

Original light switches were designed for incandescent lights at unity pf. Later
other kinds of lamps like LFL, CFL,Mercury,Sodium,MH,LED have come to stay.Will the high inrush current reduce the life of light switches?. From where can one get the inrush currents,pf,striking voltage of various kinds of bulbs of different rating?. Is there any regulation for amp rating/inrush current,striking voltage,pf,derating factor etc of light switches

 

[kbsparky]

Incandescent bulbs have high inrush current when switched on cold. The resistance of a cold filament is quite low, making the inrush current high.

Because of that, over 90% of burn-outs occur when the bulb is first switched on, blowing out the filament with a bright flash. Sometimes, this results in a tripped circuit breaker as well.

I doubt that the different power factor characteristics of ballasted CFL's would result in higher inrush currents than the lower resistance of a cold incandescent filament.

 

[iwire]

Original light switches were designed for incandescent lights at unity pf.

Light switches here in the US have been rated for many types of loads for a very long time.

404.14 Rating and Use of Snap Switches. Snap switches
shall be used within their ratings and as indicated in
404.14(A) through (E).

FPN No. 1: For switches on signs and outline lighting, see
600.6.

FPN No. 2: For switches controlling motors, see 430.83,
430.109, and 430.110.

(A) Alternating-Current General-Use Snap Switch. A
form of general-use snap switch suitable only for use on ac
circuits for controlling the following:

(1) Resistive and inductive loads, including electricdischarge
lamps, not exceeding the ampere rating of the
switch at the voltage involved

(2) Tungsten-filament lamp loads not exceeding the ampere
rating of the switch at 120 volts

(3) Motor loads not exceeding 80 percent of the ampere
rating of the switch at its rated voltage


(B) Alternating-Current or Direct-Current General-Use
Snap Switch. A form of general-use snap switch suitable for
use on either ac or dc circuits for controlling the following:

(1) Resistive loads not exceeding the ampere rating of the
switch at the voltage applied.

(2) Inductive loads not exceeding 50 percent of the ampere
rating of the switch at the applied voltage. Switches
rated in horsepower are suitable for controlling motor
loads within their rating at the voltage applied.

(3) Tungsten-filament lamp loads not exceeding the ampere
rating of the switch at the applied voltage if
T-rated.


(C) CO/ALR Snap Switches. Snap switches rated 20 amperes
or less directly connected to aluminum conductors
shall be listed and marked CO/ALR.


(D) Alternating-Current Specific-Use Snap Switches
Rated for 347 Volts. Snap switches rated 347 volts ac shall
be listed and shall be used only for controlling the loads
permitted by (D)(1) and (D)(2).

(1) Noninductive Loads. Noninductive loads other than
tungsten-filament lamps not exceeding the ampere and voltage
ratings of the switch.

(2) Inductive Loads. Inductive loads not exceeding the
ampere and voltage ratings of the switch. Where particular
load characteristics or limitations are specified as a condition
of the listing, those restrictions shall be observed regardless
of the ampere rating of the load.

The ampere rating of the switch shall not be less than
15 amperes at a voltage rating of 347 volts ac. Flush-type
snap switches rated 347 volts ac shall not be readily interchangeable
in box mounting with switches identified in
404.14(A) and (B).


(E) Dimmer Switches. General-use dimmer switches shall
be used only to control permanently installed incandescent
luminaires unless listed for the control of other loads and
installed accordingly.